The lengths of human pregnancies can be described by a Normal model with a mean of 268 days and a standard deviation of 15 days. What percentage of pregnancies can we expect will last at least 300 days?

**Solution: **Let_{}be the random number of days of pregnancy. We are looking for the following probability:

_{}

_{}

which means that 0.3830425% of pregnancies will last at least 300 days.

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